[aidenn0]

If you use an encoder to adjust your position, then you are a servo; you probably won't use a stepper motor because the main advantage to a stepper motor is that you don't need position feedback to estimate the position accurately, but a stepper motor with feedback is just as much a servomechanism as any other motor with negative feedback.

[edit]

Wikipedia tells me that there are some mechanisms that use stepper motors that run mostly open-loop with an encoder only for detecting stepper-miss. Whether or not this qualifies as a servo-mechanism is up for debate.

In any event, I seriously doubt that a sub $200 plotter is doing this, as the encoder adds to the BOM.